The present invention generally relates to semiconductor devices and more particularly to a fabrication process of a semiconductor device that uses a damascene process and a semiconductor device fabricated according to such a fabrication process.
Conventionally, improvement of operational speed has been achieved in semiconductor devices with device miniaturization achieved according to the scaling law.
On the other hand, recent high-density semiconductor integrated circuits generally use a multilayer interconnection structure for interconnecting various semiconductor elements therein. In such a multilayer interconnection, there arises a problem of signal delay caused by the stray capacitance between interconnection patterns when the semiconductor device is miniaturized excessively and the interconnection patterns in the multilayer interconnection structure approach with each other.
Thus, investigations are being made conventionally for eliminating the problem of signal delay in the multilayer interconnection structure by using a low dielectric film (so-called low-K film) such a an organic insulation film of hydrocarbon family or fluorocarbon family, in place of the SiO2 insulation film used conventionally. It should be noted that such organic insulation films generally has the dielectric constant of 2.3-2.6, while this value is lower than that of the conventional SiO2 interlayer insulation film by 40-50%. In combination therewith, use of low resistance copper (Cu) patterns is studied for the interconnection patterns in place of conventional Al patterns.
Generally, a low-dielectric film is characterized by its low density, and because of this, there remain problems such as adherence to the interconnection pattern or resistance against humidity. Because of this, it is generally practiced to use a low-K dielectric film and a Cu interconnection pattern to the lower part of the multilayer interconnection structure where the problem of signal delay appears conspicuously while continuously using the conventional SiO2 insulation film characterized by excellent adherence in the upper part of the multilayer interconnection structure where the interconnection patterns are formed with relatively sparse interval.